1. Field of the Invention
The present relates generally to medical apparatus and methods. More particularly, the present invention relates to methods and apparatus for creating isolated working spaces within the lumen or a blood vessel to facilitate forming end-to-side anastomoses.
Coronary artery bypass graft (CABG) surgery remains one of the most common treatment for coronary artery disease in the United States and other developed countries. Vein grafts, typically harvested from the patient""s legs are connected to the aorta and then to the coronary arteries beyond diseased regions. This procedure is typically performed with the patient""s heart stopped after initiation of cardiopulmonary bypass. Cardiopulmonary bypass and stopping the heart has been associated with stroke as well as heart muscle damage. To reduce these risks, surgeons have developed techniques to perform CABG while the heart is still beating avoiding cardiopulmonary bypass.
CABG using beating heart technique is performed in the following manner. After obtaining the appropriate level of anesthesia, the surgeon makes an incision over the sternum after which the sternum is divided. The pericardial sac is opened and the patient""s aorta and heart are identified and examined. Simultaneously, saphenous veins are harvested from the patient""s legs. The surgeon clamps the aorta with a side biting clamp, partially occluding the aorta. A small incision in the aorta is made after which hole punch device is used to make an appropriate size hole, typically 4-6 mm in diameter. The saphenous vein is then sutured onto the aorta. Similarly, the site on the coronary artery where the distal anastomosis will be placed is identified after which an incision is made and the vein sutured.
Clamping the aorta using the side biting technique as well as using cross clamp technique as used during cardiopulmonary bypass, is associated with trauma to the aorta as well as releasing plaque in to the circulation possibly causing a stroke.
In order to at least partially overcome these difficulties, U.S. Pat. No. 5,944,730 proposes to use a device which can create a working space on the interior surface of a blood vessel wall without interrupting the flow of blood through the blood vessel, such as the aorta. The device comprises an inverted cone at the end of a shaft, where the cone can be deployed in the manner of an umbrella. The peripheral lip of the cone is then drawn proximally against the interior wall to isolate the working space from blood flow. The device is useful in stopped heart procedures as well as in beating heart procedures.
Although promising, the device of U.S. Pat. No. 5,944,730, itself suffers from certain limitations. The inverted cone is a rather rigid structure which may have difficulty mating and sealing against the interior surface of the aorta or the blood vessel. Moreover, the relatively rigid nature of the cone can itself disrupt and dislodge plaque from the interior of the aorta, presenting an immediate risk of stroke and peripheral vascular damage since circulation has not been stopped. Additionally, the mechanical structure of the device will require a relatively large profile, making removal of the device after an end-to-side anastomosis has been formed somewhat difficult. In short, the device of U.S. Pat. No. 5,944,730, is complex, cumbersome, and difficult to deploy.
For these reasons, it would be desirable to provide improved and alternative methods and devices for forming working spaces within the aorta and other blood vessels without the need to stop blood flow through the blood vessel. In particular, it would be desirable to create isolated regions or xe2x80x9cworking spacesxe2x80x9d on the aorta wall which are suitable for preparing an anastomotic hole which can subsequently be sutured or otherwise attached to a saphenous vein or other graft. The devices used to form such working spaces should be capable of forming tight seals with the inner wall of the aorta with minimum trauma and risk of emboli release. The devices should have a low profile to facilitate both introduction to the aorta or the blood vessel as well as withdrawal from the blood vessel lumen after the anastomosis has been formed. At least some of these objectives will be met by the inventions described hereinafter.
2. Description of the Background Art
U.S. Pat. No. 5,944,730, describes a device having an inverted shell that is mechanically deployed within a blood vessel lumen to create a working space for performing an end-to-side anastomosis. The device has a relatively large profile and requires an incision for initial placement in the blood vessel. The deployable shell would not be expected for form an optimum seal with the interior blood vessel wall after deployment.
Other devices for locating and/or creating isolated regions within blood vessels for anastomotic attachments are described in EP 894 475 and PCT publications WO 97/47261 and WO 95/17127.
Devices for sealing punctures in blood vessel walls, atrial septums, and the like, are described in U.S. Pat. Nos. 4,744,364; 4,794,928; 5,192,301; 5,222,974; 5,330,446; 5,342,393; 5,350,399; 5,383,896; 5,496,332; 5,593,422; 5,630,833; 5,690,674; 5,700,277; 5,766,220; 5,782,860; 5,922,009; and 5,951,589.
The present invention provides methods, apparatus, and kits for forming an anastomotic site in the wall of a blood vessel or other body lumen, usually an artery, and more usually the aorta. The anastomotic site will be useful for connection of a graft vessel, typically a portion of the patient""s own saphenous vein which is harvested earlier in the procedure. Other conduits which may be harvested include the brachiocephalic vein as well as the radial and internal mammary arteries. In addition to the use of harvested veins, grafts formed from ePTFE, dacron, and the like, may also find use under certain circumstances. Other body lumens where anastomotic sites may be formed using the present invention include the intestines, both small and large.
The working surface formed by the methods of the present invention will be a small volume within the lumen of the blood vessel which is isolated from blood flow which would otherwise pass through that space. The working space will usually be circular or annular in the region where it interfaces with the inner wall of the blood vessel, usually having a diameter in the range from 3 mm to 10 mm, more usually from 4 mm to 6 mm. As described in more detail below, the working space will be defined by an inflatable barrier which typically has a hemispherical or ovoid geometry. The volume of the working space will generally be from 7 mm3 to 250 mm3, usually from 20 mm3 to 50 mm3. Once formed on the inner wall of the blood vessel, the working space will be available for any desired purpose. Usually, the space will be used initially to permit cutting or punching of an anastomotic hole through the blood vessel wall, where the hole will open wholly into the working space. Additionally, after the anastomotic hole is formed, the working space will usually be used to accommodate the needles used to suture a distal end of the graft vessel to the anastomotic hole in the blood vessel wall.
Of particular interest to the present invention, the working space will be formed by an inflatable barrier which has a recessible surface which is positioned or engaged against the inner surface of the blood vessel wall. The inflatable barrier will have a very low profile prior to inflation, typically having an outer diameter below 2 mm, preferably below 1.5 mm. Additionally, after deflation, the inflatable barrier will again have a low profile to facilitate withdrawal from the blood vessel through which the anastomosis is being formed. The recessible surface may be performed as part of the geometry of the inflatable barrier. That is, the recession may form as the barrier is inflated. In such cases, the recession may be concave, annular, or have some other complex shape which accommodates a particular purpose. Alternatively, the recessible surface may comprise an elastic or otherwise deformable region of the inflatable barrier where the region can be deformed by a separate tool after inflation, such as by using a separate needle shield tool as described below.
In a first aspect, methods according to the present invention will form an anastomotic site in a blood vessel having a wall with an outer surface, an inner surface, and an interior lumen. The inflatable barrier is positioned so that its concave surface lies against the inner surface of the blood vessel wall. The balloon will preferably be made from an elastomeric or other conformable material so that it can conform to and seal tightly against the inner surface of the wall. After the barrier is inflated, the isolated working space is created interior to the inner surface of the blood vessel wall. A hole may then be cut through the wall into the working space to create the anastomotic site, while the site remains isolated from flowing blood by the inflated barrier. In a first embodiment of the method, the barrier is positioned while in a deflated condition through a penetration in the blood vessel wall into the lumen. The barrier may be introduced directly through a separately formed incision in the blood vessel wall, or may be positioned using an access needle in a Seldinger approach. In a Seldinger approach, the inflatable barrier is positioned within the Seldinger needle, and the needle withdrawn proximally over the barrier after the barrier has been properly positioned. After positioning, the barrier is inflated, and the concave surface of the barrier drawn backwardly against the inner surface of the blood vessel wall to locate the working space over the initial penetration. Optionally, after the Seldinger needle is removed, it may be exchanged for a removal sheath which remains in place over the catheter to facilitate removal of the inflatable barrier at the end of the procedure. In cases where the catheter is introduced through a Seldinger needle and/or a removal sheath is placed over the catheter, it will be necessary that the catheter have a removal inflation hub at its distal end to permit introduction and withdrawal of the devices thereover.
Once the working space is established, the anastomotic hole may be formed, conveniently using a conventional cutting die. Optionally, the cutting die can be modified in some way to accommodate presence of the catheter extending outwardly through the anastomotic hole. The catheter must, of course, remain in place so that the physician can continue to pull proximally on the catheter in order to maintain the desired sealing and isolation of the working space. Thus, the anastomotic hole will have to be formed in such a way as to avoid interference from the catheter. One way of achieving such non-interference is to provide a channel in the side of an otherwise conventional anastomotic hole punch in order to accommodate the presence of the catheter.
Once the anastomotic hole is formed, the methods of the present invention will usually further comprise attaching a distal end of a graft vessel to the anastomotic site, typically using conventional manual suturing. After the anastomotic connection is substantially complete, the catheter and deflated inflatable barrier may be removed from between the graft and the aorta, and the suture attachment tightened and completed quickly after the site is again exposed to flowing blood.
In an alternative protocol according to the present invention, the inflatable barrier may be positioned through a first penetration in the blood vessel wall and into the blood vessel lumen. The barrier is then advanced axially through the blood vessel lumen away from the first penetration. Usually, the second penetration is formed at the location of the working space and a tether passed through the second penetration. The tether is attached to the inflatable barrier through the second penetration, and thus pulling on the tether will draw the inflatable barrier against the inner surface of the blood vessel at the working site. The balloon is inflated and the barrier is further drawn against the arterial wall at the working site to the desired tension by pulling on the tether. Presence of the tether, which may be a single filament or length of suture, is advantageous in that it presents little interference to formation of the anastomotic hole and subsequent suturing of the graft to the hole. Moreover, both the inflatable barrier and the tether may be withdrawn proximally so that they pass outwardly through the second penetration, thus allowing the anastomosis to be substantially completed before deflation of the inflatable barrier. The tether which remains within the newly anastomosed site can be readily withdrawn inward without disturbing the anastomosis.
In a particular embodiment of the alternative protocol, the inflatable barrier is deployed by first passing a curved needle in through the first penetration and then outward through the second penetration in the blood vessel wall. The needle is attached to the tether which is used to draw and position the inflatable barrier at the target anastomotic site. Usually, the inflatable barrier will be mounted at the end of a shaft, and the shaft will be curved to facilitate locating the concave surface of the barrier back against the inner wall of the blood vessel.
In the second protocol, after the inflatable barrier has been positioned, the anastomotic hole may be formed by introducing a cutting die over or adjacent to the tether. If the cutting die is advanced adjacent to the tether, a channel may optionally be formed in the cutting die to accommodate the tether as the cutting die is advanced.
As with the first protocol, after the anastomotic hole is formed, the distal end of the graft vessel will be sutured or otherwise attached to the anastomotic hole while the tether remains in place between the newly placed graft vessel in the hole. As described above, however, the tether will then be withdrawn outwardly through the first penetration (not the anastomotic hole) in order to lessen interference with the anastomosis which has just been created.
As the isolation barrier will usually be in place as the graft vessel is sutured (anastomosed) to the aorta or the blood vessel, it is desirable that the inner surface of the inflatable barrier be protected. This is particularly in the case when the inflatable barrier is an elastomeric balloon formed from conventional materials, such as silicone rubber, latex, or the like. In a first instance, the balloon may be protected by forming a penetration-resistant barrier over at least a portion of the concave surface. In this way, after the barrier is deployed, accidental needle penetration through the barrier will be inhibited. In a second instance, a separate needle penetration guard may be introduced through the penetration and/or anastomotic hole prior to either cutting or suturing. For example, the guard may comprise a shield formed at the end of a separate shaft so that the shield can be positioned adjacent to the barrier when needed to protect the barrier.
In a further optional aspect of the methods of the present invention, concave surface of the barrier will be drawn against the inner surface of the blood vessel wall by pulling outwardly on the catheter body. In such instances, the catheter may be constructed to yield in response to axial tension, i.e., to stretch as the inflatable shield is drawn against the inner surface of the blood vessel wall. Such stretching will modulate the force applied against the inner surface of the blood vessel wall. This will allow the inflatable barrier to be drawn against the arterial wall at the working site with the proper tension, thus reducing vessel trauma. In a further optional aspect, after the catheter has been positioned, the anastomotic hole formed and hemostasis established, such stretchable tool shafts can be held in place by a mechanical apparatus usually fixed to the sternal retractor.
Apparatus according to the present invention for isolating a working space in a blood vessel having a wall with an outer surface, an inner surface, and an interior lumen comprise an inflatable barrier and means for introducing and deploying the inflatable barrier through penetration in the blood vessel wall. The inflatable barrier will have a recessible surface, as previously described, which is adapted to conform to and seal against the inner surface of the blood vessel wall to define the desired working space.
The means for introducing can take a variety of forms, but will usually comprise a shaft having a proximal end, a distal end, and an inflation lumen therethrough. The inflatable barrier is attached at or near the distal end of the shaft, and the recessible surface of the barrier may be disposed in either a proximal direction (so that the barrier may be deployed by pulling backwardly on the shaft to engage the surface against the blood vessel wall) or distally (so that the recessible surface may be deployed by advancing the shaft forwardly). The shaft itself may be straight, which is particularly useful in those embodiments where the barriers be deployed at a proximal direction. In some instances, at least a portion of the straight shafts will be formed so that they yield to axial tension so that the shaft can stretch as it is being deployed. Alternatively, when the inflatable barrier is to be deployed with the recessible surface disposed distally, the shaft will usually be curved so that the barrier can be engaged against the inner wall of the blood vessel by pushing the shaft forwardly and upwardly against the desired location, where the shaft is introduced through a penetration spaced-apart from the desired location. Optionally, in at least the straight shaft embodiments, the apparatus may further comprise a guidewire extending distally from the distal tip of the shaft. The guidewire is advantageous because it allows for the advancement of the catheter in a blind fashion with minimal trauma to the luminal surface of the arterial wall.
As an alternative or an addition to the shafts described above, the introducing means may comprise a tether attached to the concave surface of the barrier. In such cases, the tether will be adapted to be passed through a penetration in the blood vessel wall to permit positioning of the inflatable barrier by drawing outwardly on the tether. While the tether itself may be all that is needed to deploy the barrier, a separate curved shaft will usually be joined to the inflatable barrier in addition to the tether, as described in the specific embodiments below.
Preferably, the introducing means comprising a tether will further comprise a curved needle attached to a distal end of the tether. In this way, the curved needle can be introduced to the blood vessel to form a first penetration and an axially spaced-apart second penetration. The tether can then be drawn through both penetrations in order, and the tether then used to draw the concave surface of the inflatable barrier against the desired anastomotic site which is located adjacent to the second penetration. The first penetration will then be available to accommodate a positioning and an inflation shaft, as described above in connection with the methods of the present invention.
The inflatable barriers of the apparatus of the present invention will typically comprise balloons, more typically elastomeric balloons which present minimum risk of trauma to the blood vessel and which can readily conform to the interior surface of the aorta or other blood vessel. The inflatable balloons will have a xe2x80x9crecessible surfacexe2x80x9d which provides the isolated working space. Most simply, the barrier can have a cup-shaped geometry with the interior of the cup defining the working space. Alternatively, the geometry or contour of the inflated balloon may be complex and present a trough or channel at the margins of the anastomotic hole to provide a working space for the anastomotic or other subsequent procedure. In another embodiment the balloon may have a flat or even convex configuration where the working space is created by compressing the balloon with the penetration shield or other rigid tool. The shape and volume of the working space defined by the cup is generally as described above in connection with the methods of the present invention. The inflatable elastomeric balloon will optionally comprise a needle penetration shield formed over at least a portion of the concave surface. The shield will typically be formed from a penetration-resistant polymer, such as polyimide. Alternatively, if a separate needle penetration barrier is to be used, the elastomeric balloon need not have a separate penetration-resistant layer. It will be appreciated that elimination of the penetration-resistant barrier may be desirable in order to produce the profile of the balloon in its non-inflated condition. Alternatively, inclusion of the penetration-resistant barrier is desirable in order to reduce the risk of accidentally damaging the balloon.
The present invention further comprises systems and kits. A system according to the present invention comprises any of the straight shaft isolation barriers in combination with a sheath. The sheath may be useful to facilitate removal, as described above. Alternatively, in the case of shafts which can stretch or otherwise deform, the sheath may be useful to facilitate introduction of the shaft (as well as possible removal of the shaft).
Additional kits according to the present invention comprise the apparatus described above in combination with a tool comprising a shaft and a needle penetration shield. The tool may thus be separately deployed to protect the balloons of the apparatus from damage during anastomosis procedures.
Kits according to the present invention will comprise an inflatable barrier, generally as described above, in combination with instructions for use setting forth any of the methods described above. The kits may further comprise the removal sheath, introduction sheath, penetration shield tool, anastomotic hole punch, inflation syringe, scalpel, or other system components which may be used for performing the methods of the present invention. Usually, the kit will comprise conventional medical device packaging, such as a box, tube, tray, pouch, or the like, and the instructions for use may be printed on a separate instruction sheet and/or on the packaging itself. The system components will be maintained within the packaging, typically being maintained in a sterile condition.